Full Idea
By matter I mean that which in itself is neither a particular thing nor a certain quantity nor assigned to any other of the categories by which being is determined.
Gist of Idea
Matter is neither a particular thing nor a member of a determinate category
Source
Aristotle (Metaphysics [c.324 BCE], 1029a20)
Book Reference
Aristotle: 'The Basic Works of Aristotle', ed/tr. McKeon,Richard [Modern Library Classics 2001], p.785
A Reaction
This seems to be the classic definition of matter in Aristotle. He doesn't say here that matter has an inferior mode of existence, but elsewhere he says that it is potential rather than actual, which seems to confiscate its passport.